1. Field of the Invention
The present invention relates to a method for stabilizing pranoprofen having anti-inflammatory activity, in an aqueous solution of pranoprofen, and to a liquid preparation comprising, as an active ingredient, pranoprofen which is stabilized by adding an antioxidant.
2. Description of Related Art
Pranoprofen having a chemical name of .alpha.-methyl-5H-1!benzopyrano2,3-b!pyridine-7-acetic acid exhibits prominent anti-inflammatory action, analgesic action and antipyretic action. It is a non-steroidal anti-inflammatory drug having a wider safety margin, and is commercially available by the product name of Niflan (trademark). The properties and production method thereof are described in U.S. Pat. No. 3,931,295.
There has also been proposed an eye drop containing pranoprofen as an anti-inflammatory active ingredient and boric acid as an isotonizing agent, as being useful for, in particular, herpesvirus eye diseases (U.S. Pat. No. 4,607,038).
However, pranoprofen is unstable in an aqueous solution state, particularly to light and is gradually decomposed during long-term preservation.
It is therefore an object of the present invention to provide a method for stabilizing pranoprofen in an aqueous solution state.
Another object of the present invention is to provide an aqueous solution of pranoprofen, wherein decomposition of pranoprofen is suppressed.